OBJECTIVES:
To review the clinical course, complication rates, and mid-term functional outcomes associated with the treatment of displaced femoral neck stress fractures (FNSFs).

DESIGN:
Retrospective Case Series.

SETTING:
Military Tertiary Referral Center.

PATIENTS:
Twenty-one operatively treated displaced FNSFs between 2002 and 2015.

INTERVENTION:
Urgent reduction and fixation was performed. If nonunion developed, an intertrochanteric osteotomy was performed.

MAIN OUTCOME MEASUREMENTS:
Nonunion, osteonecrosis (ON) of the femoral head, conversion to arthroplasty, modified Harris Hip Score, pain score, and Hip Outcome Score (HOS).

RESULTS:
Two (9.1%) patients developed nonunion. Both united after revision with intertrochanteric osteotomy. ON developed in one patient (4.8%) who was converted to arthroplasty. Average pain score at final follow-up was 2.0 (range 0-5). Average Modified Harris Hip Score was 84 (range 54-100). Average HOS Activities of Daily Living subscale was 80.9 (range 45.6-100). Average HOS Sport subscale was 69.8 (range 27.8-100). Larger displacement on injury films correlated with lower Modified Harris Hip Scores (P = 0.048) and lower HOS Sports Subscale Single Assessment Numeric Evaluation (P = 0.023). The need for an open reduction trended toward being a risk factor for nonunion (P = 0.081).

CONCLUSIONS:
This study represents the largest series of patients undergoing urgent surgery for displaced FNSFs. Nonunion and ON is found at a similar rate to what is reported in the young traumatic literature. Pain and outcome scores compare favorably to other hip pathology in young adults. Initial injury severity is variably correlated to final outcome scores.

LEVEL OF EVIDENCE:
Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.





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